Hello, I've detected that there is soft a grid pattern applied to all images when I try to use them to fill full page with CSS background-image output. I've tried with JPG/PNG.

I've attached zoomed version of the image (printscreen from generated PDF), it has a grid (you need to look closely).
When I use same image with attribute it works fine.

For my purpose, I need to use background-image as CSS, because I need all my pages to have background applied, so is not suitable.

Can you point me in the direction on how to fix this?

Than you very much for your time.